Chemically strengthened bond between thermally stable polycrystalline hard materials and braze material

ABSTRACT

Chemical methods, optionally in combination with physical methods, may be used to increase the strength of the bond formed by a braze material between a polycrystalline material and a hard composite. Such polycrystalline materials brazed to hard composites may be found in various wellbore tools include drill bit cutters. An exemplary method may include forming a bonding layer on a bonding surface of a polycrystalline material body that comprises a hard material, the bonding surface opposing a contact surface of the polycrystalline material body, and the bonding layer substantially formed by a [111] crystal structure of the hard material, a [100] crystal structure of the hard material, or a combination thereof; and brazing the bonding layer to a hard composite using a braze material.

BACKGROUND

The present application relates to bonding hard composites topolycrystalline materials, including but not limited to, polycrystallinediamond (“PCD”) materials and thermally stable polycrystalline (“TSP”)materials.

Drill bits and components thereof are often subjected to extremeconditions (e.g., high temperatures, high pressures, and contact withabrasive surfaces) during subterranean formation drilling or miningoperations.

Hard materials like diamond, cubic boron nitride, and silicon carbideare often used at the contact points between the drill bit and theformation because of their wear resistance, hardness, and ability toconduct heat away from the point of contact with the formation.

Generally, such hard materials are formed by combining particles of thehard material and a catalyst, such that when heated the catalystfacilitates growth and/or binding of the hard material so as to bind theparticles together to form a polycrystalline material. However, thecatalyst remains within the body of the polycrystalline material afterforming. Because the catalyst generally has a higher coefficient ofthermal expansion than the hard material, the catalyst can causefractures throughout the polycrystalline material when thepolycrystalline material is heated (e.g., during brazing to attach thepolycrystalline material to the drill bit or a portion thereof like acutter or during operation downhole). These fractures weaken thepolycrystalline material and may lead to a reduced lifetime for thedrill bit.

To mitigate fracturing of the polycrystalline material, it is common toremove at least some of the catalyst, and preferably most of thecatalyst, before exposing the polycrystalline material to elevatedtemperatures. Polycrystalline materials that have a substantial amountof the catalyst removed are referred to as thermally stablepolycrystalline (“TSP”) materials.

Specifically for drill bits, TSP materials are often bonded to anothermaterial (e.g., a hard composite like tungsten carbide particlesdispersed in a copper binder) to allow the more expensive TSP materialsto be strategically located at desired contact points with theformation. However, separation of the TSP material and the surface towhich it is bonded during operation reduces the efficacy and lifetime ofthe drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of theembodiments, and should not be viewed as exclusive embodiments. Thesubject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIG. 1 is a cross-sectional view of a matrix drill bit having a matrixbit body formed by a hard composite material.

FIG. 2 is an isometric view of the matrix drill bit that includespolycrystalline material cutters according to at least some embodimentsof the present disclosure.

FIGS. 3A and 3B are cross-sectional views of polycrystalline materialcutters according to at least some embodiments of the presentdisclosure.

FIGS. 4A and 4B illustrate a side-view and a top view of a mask disposedon the bonding surface of a polycrystalline material body.

FIG. 5 is a schematic drawing showing one example of a drilling assemblysuitable for use in conjunction with the matrix drill bits that includepolycrystalline material cutters of the present disclosure.

DETAILED DESCRIPTION

The present application relates to bonding polycrystalline materials tohard composites when forming abrasive components of downhole tools(e.g., cutters for use in drill bits). More specifically, the presentapplication relates to chemical methods, optionally in combination withphysical methods, for increasing the strength of the bond formed by abraze material between the polycrystalline materials and the hardcomposite. The teachings of this disclosure can be applied to anydownhole tool or component thereof where polycrystalline materials arebrazed to a hard composite. Such tools may include tools for drillingwells, completing wells, and producing hydrocarbons from wells. Examplesof such tools include cutting tools, such as drill bits, reamers,stabilizers, and coring bits; drilling tools, such as rotary steerabledevices and mud motors; and other tools used downhole, such as windowmills, packers, tool joints, and other wear-prone tools.

FIG. 1 is a cross-sectional view of a matrix drill bit 20 having amatrix bit body 50 formed by a hard composite material 131. An exemplaryhard composite material may include, but not be limited to, reinforcingparticles dispersed in a binder material. As used herein, the term“matrix drill bit” encompasses rotary drag bits, drag bits, fixed cutterdrill bits, and any other drill bit having a matrix bit body and capableof incorporating the teachings of the present disclosure.

For embodiments such as those shown in FIG. 1, the matrix drill bit 20may include a metal shank 30 with a metal blank 36 securely attachedthereto (e.g., at weld location 39). The metal blank 36 extends intomatrix bit body 50. The metal shank 30 includes a threaded connection 34distal to the metal blank 36.

The metal shank 30 and metal blank 36 are generally cylindricalstructures that at least partially define corresponding fluid cavities32 that fluidly communicate with each other. The fluid cavity 32 of themetal blank 36 may further extend longitudinally into the matrix bitbody 50. At least one flow passageway (shown as two flow passageways 42and 44) may extend from the fluid cavity 32 to exterior portions of thematrix bit body 50. Nozzle openings 54 may be defined at the ends of theflow passageways 42 and 44 at the exterior portions of the matrix bitbody 50.

A plurality of indentations or pockets 58 are formed in the matrix bitbody 50 and are shaped or otherwise configured to receive cutters.

FIG. 2 is an isometric view of the matrix drill bit that includes aplurality of cutters 60 according to at least some embodiments of thepresent disclosure. As illustrated, the matrix drill bit 20 includes themetal blank 36 and the metal shank 30, as generally described above withreference to FIG. 1.

The matrix bit body 50 includes a plurality of cutter blades 52 formedon the exterior of the matrix bit body 50. Cutter blades 52 may bespaced from each other on the exterior of the matrix bit body 50 to formfluid flow paths or junk slots 62 therebetween.

As illustrated, the plurality of pockets 58 may be formed in the cutterblades 52 at selected locations. A cutter 60 may be securely mounted(e.g., via brazing) in each pocket 58 to engage and remove portions of asubterranean formation during drilling operations. More particularly,each cutter 60 may scrape and gouge formation materials from the bottomand sides of a wellbore during rotation of the matrix drill bit 20 by anattached drill string.

A nozzle 56 may be disposed in each nozzle opening 54. For someapplications, nozzles 56 may be described or otherwise characterized as“interchangeable” nozzles.

FIGS. 3A and 3B are cross-sectional views of exemplary cutters 60 a and60 b, respectively, according to at least some embodiments of thepresent disclosure. The cutter 60 is formed by a polycrystallinematerial body 64 having a bonding layer 76 bonded to a hard compositebody 66 with braze 68. The bonding layer 76 may be substantially formedby [111] crystal structures, [100] crystal structures, or both of thecorresponding hard material. That is, at least 50% of the bonding layer76 may have or otherwise exhibit a [111] crystal structure, a [100]crystal structure, or a combination thereof. Without being limited bytheory, it is believed that [111] crystal faces and [100] crystal facesmay have greater bonding strength to braze materials (e.g., alloys of atleast two of silver, copper, nickel, titanium, vanadium, phosphorous,silicon, aluminum, molybdenum and the like), which may prove useful inmitigating separation of the polycrystalline material body 64 and thehard composite body 66 during use downhole.

By way of nonlimiting example, the bonding layer 76 may be substantiallyformed by a [111] crystal structure, and the braze may be acopper-silicon alloy with titanium as the active element. By way ofanother nonlimiting example, the bonding layer 76 may be substantiallyformed by a [100] crystal structure, and the braze may be acopper-silicon eutectic alloy with titanium as the active element.

Examples of polycrystalline materials suitable for use as thepolycrystalline material body 64 may include, but are not limited to,polycrystalline diamond, polycrystalline cubic boron nitride,polycrystalline silicon carbide, TSP diamond, TSP cubic boron nitride,TSP silicon carbide, and the like. As described in more detail above, apolycrystalline material is formed by subjecting small grains of a hardmaterial (e.g., diamond, cubic boron nitride, and silicon carbide) thatare randomly oriented and other starting materials (e.g., catalyst) toultrahigh pressure and temperature conditions. Then, the TSP materialmay be formed by removing at least a portion of the catalyst from thestructure.

The resultant polycrystalline material body 64 may define and otherwiseprovide a bonding surface 70 opposite a cutting surface 72. Because ofthe forming or synthesis method, the surfaces 70,72 have no preferentialcrystal structure. As illustrated in FIG. 3A, the bonding layer 76 maybe formed on the bonding surface 70 of the polycrystalline material body64, additional details provided herein. Alternatively, in FIG. 3B, arefractory nitride layer 80 may be deposited on the bonding surface 70of the polycrystalline material body 64. Then, the bonding layer 76 maybe formed on the refractory nitride layer 80. The refractory nitridelayer 80 may facilitate forming or synthesizing the preferred diamondcrystal structure of the bonding layer 76.

The hard composite body 66 may define and otherwise provide a bondingsurface 74. The bonding layer 76 and the bonding surface 74 of the hardcomposite body 66 may be coupled and otherwise bonded together with thebraze 68. Further, once the polycrystalline material body 64 and thehard composite body 66 are bonded, the cutting surface 72 of thepolycrystalline material body 64 is appropriately located such that oncethe cutter 60 is assembled in a drill bit the cutting surface 72 ispositioned to engage the formation during use of the drill bit.

In some embodiments, the bonding layer 76 may be formed by chemicalvapor deposition where temperature, gas composition, and pressure may beused to preferentially form [111] crystal structures, [100] crystalstructures, or a combination thereof. For example, diamond [111] crystalstructures and diamond [100] crystal structures may be formed byreacting hydrogen, oxygen, and a carbon-containing gas (e.g., methane)in a hydrogen plasma where the bonding surface 70 or the refractorynitride layer 80 temperature is at 600° C. to 1100° C. The relativeconcentrations of hydrogen, oxygen, and the carbon-containing gas may be200 parts to 250 parts hydrogen, 0.5 parts to 3 parts oxygen, and 3parts to 8 parts carbon-containing gas. In some embodiments,preferentially forming [111] crystal structures may be achieved bymaintaining a total pressure 30 torr or greater. In some embodiments,preferentially forming [100] crystal structures may be achieved bymaintaining a total pressure less than 30 torr. Generally, when formingthe bonding layer 76, the bonding surface 70 or the refractory nitridelayer 80 may be heated to the desired temperature, the gas pressure withhydrogen only may be achieved, and the plasma may be initiated (e.g.,using microwave power). Then, flow of the carbon-containing gas maybegin followed by the oxygen. Once all gases are flowing (where relativeflow rates may be used to achieve desired gas concentrations in thereactor), the reaction may be allowed to proceed for a desired amount oftime (e.g., 1 hour to 24 hours) depending on the desired thickness ofthe bonding layer 76.

In some instances, the bonding layer 76 may have a thickness of 10microns to 250 microns, including subsets therebetween (e.g., 50 micronsto 200 microns, 100 microns to 250 microns, or 100 microns to 150microns).

In some embodiments when forming the bonding layer 76 or the refractorynitride layer 80, a mask may be used to so that the bonding layer 76 orthe refractory nitride layer 80 is formed only on a portion thereof.FIGS. 4A and 4B illustrate a side-view and a top view, respectively, ofa mask 78 disposed on the bonding surface 70 of a polycrystallinematerial body 64, which alternatively could be the refractory nitridelayer 80 deposited on the polycrystalline material body 64. As best seenin FIG. 4B, the mask 78 covers only a portion of the bonding surface 70such that the bonding layer 76 may form on only the exposed portions ofthe bonding surface 70. Such masking may be beneficial for producingreliefs (i.e., protrusions), which results in an uneven bonding layer76. The uneven bonding layer 76 may provide additional surface area thatmay be contacted with the braze material 68, and thereby potentiallyenhance the strength of the braze bond.

Masks may be formed by any known methods (e.g., photomasking) withmaterials suitable for withstanding further processing ensuring theformation of the bonding layer 76. Examples of materials suitable foruse as a mask may include, but are not limited to, silicon oxide,metallic films, photoresist materials, and the like.

Masks may be used to form any pattern, for example, squares, concentriccircles, stripes, and the like.

Examples of hard composites used to form the hard composite body 66described herein may be formed by reinforcing particles dispersed in abinder material. Exemplary binder materials may include, but are notlimited to, copper, nickel, cobalt, iron, aluminum, molybdenum,chromium, manganese, tin, zinc, lead, silicon, tungsten, boron,phosphorous, gold, silver, palladium, indium, any mixture thereof, anyalloy thereof, and any combination thereof. Nonlimiting examples ofbinder materials may include copper-phosphorus,copper-phosphorous-silver, copper-manganese-phosphorous, copper-nickel,copper-manganese-nickel, copper-manganese-zinc,copper-manganese-nickel-zinc, copper-nickel-indium,copper-tin-manganese-nickel, copper-tin-manganese-nickel-iron,gold-nickel, gold-palladium-nickel, gold-copper-nickel,silver-copper-zinc-nickel, silver-manganese, silver-copper-zinc-cadmium,silver-copper-tin, cobalt-silicon-chromium-nickel-tungsten,cobalt-silicon-chromium-nickel-tungsten-boron,manganese-nickel-cobalt-boron, nickel-silicon-chromium,nickel-chromium-silicon-manganese, nickel-chromium-silicon,nickel-silicon-boron, nickel-silicon-chromium-boron-iron,nickel-phosphorus, nickel-manganese, copper-aluminum,copper-aluminum-nickel, copper-aluminum-nickel-iron,copper-aluminum-nickel-zinc-tin-iron, and the like, and any combinationthereof. Exemplary reinforcing particles may include, but are notlimited to, particles of metals, metal alloys, metal carbides, metalnitrides, diamonds, superalloys, and the like, or any combinationthereof. Examples of reinforcing particles suitable for use inconjunction with the embodiments described herein may include particlesthat include, but not be limited to, nitrides, silicon nitrides, boronnitrides, cubic boron nitrides, natural diamonds, synthetic diamonds,cemented carbide, spherical carbides, low alloy sintered materials, castcarbides, silicon carbides, boron carbides, cubic boron carbides,molybdenum carbides, titanium carbides, tantalum carbides, niobiumcarbides, chromium carbides, vanadium carbides, iron carbides, tungstencarbides, macrocrystalline tungsten carbides, cast tungsten carbides,crushed sintered tungsten carbides, carburized tungsten carbides,steels, stainless steels, austenitic steels, ferritic steels,martensitic steels, precipitation-hardening steels, duplex stainlesssteels, ceramics, iron alloys, nickel alloys, chromium alloys,HASTELLOY® alloys (nickel-chromium containing alloys, available fromHaynes International), INCONEL® alloys (austenitic nickel-chromiumcontaining superalloys, available from Special Metals Corporation),WASPALOYS® (austenitic nickel-based superalloys, available from UnitedTechnologies Corp.), RENE® alloys (nickel-chrome containing alloys,available from Altemp Alloys, Inc.), HAYNES® alloys (nickel-chromiumcontaining superalloys, available from Haynes International), INCOLOY®alloys (iron-nickel containing superalloys, available from Mega Mex),MP98T (a nickel-copper-chromium superalloy, available from SPSTechnologies), TMS alloys, CMSX® alloys (nickel-based superalloys,available from C-M Group), N-155 alloys, any mixture thereof, and anycombination thereof.

FIG. 5 is a schematic showing one example of a drilling assembly 200suitable for use in conjunction with matrix drill bits that include thecutters of the present disclosure (e.g., cutter 60 of FIGS. 2-3). Itshould be noted that while FIG. 5 generally depicts a land-baseddrilling assembly, those skilled in the art will readily recognize thatthe principles described herein are equally applicable to subseadrilling operations that employ floating or sea-based platforms andrigs, without departing from the scope of the disclosure.

The drilling assembly 200 includes a drilling platform 202 coupled to adrill string 204. The drill string 204 may include, but is not limitedto, drill pipe and coiled tubing, as generally known to those skilled inthe art apart from the particular teachings of this disclosure. A matrixdrill bit 206 according to the embodiments described herein is attachedto the distal end of the drill string 204 and is driven either by adownhole motor and/or via rotation of the drill string 204 from the wellsurface. As the drill bit 206 rotates, it creates a wellbore 208 thatpenetrates the subterranean formation 210. The drilling assembly 200also includes a pump 212 that circulates a drilling fluid through thedrill string (as illustrated as flow arrows A) and other pipes 214.

One skilled in the art would recognize the other equipment suitable foruse in conjunction with drilling assembly 200, which may include, but isnot limited to, retention pits, mixers, shakers (e.g., shale shaker),centrifuges, hydrocyclones, separators (including magnetic andelectrical separators), desilters, desanders, filters (e.g.,diatomaceous earth filters), heat exchangers, and any fluid reclamationequipment. Further, the drilling assembly may include one or moresensors, gauges, pumps, compressors, and the like.

Embodiments disclosed herein include:

A. a method that includes forming a bonding layer on a bonding surfaceof a polycrystalline material body that comprises a hard material, thebonding surface opposing a contact surface of the polycrystallinematerial body, and the bonding layer substantially formed by a [111]crystal structure of the hard material, a [100] crystal structure of thehard material, or a combination thereof; and brazing the bonding layerto a hard composite using a braze material;

B. a method that includes depositing a refractory nitride layer on abonding surface of a polycrystalline material body that comprises a hardmaterial, the bonding surface opposing a contact surface of thepolycrystalline material body; forming a bonding layer on the refractorynitride layer, the bonding layer substantially formed by a [111] crystalstructure of the hard material, a [100] crystal structure of the hardmaterial, or a combination thereof; and brazing the bonding layer to ahard composite using a braze material; and

C. a cutter that includes a polycrystalline material body having abonding surface opposing a contact surface; a bonding layer disposed onthe bonding surface, the bonding layer substantially formed by a [111]crystal structure, a [100] crystal structure, or a combination thereof;and a hard composite bound to the bonding layer opposite thepolycrystalline material body with a braze material;

D. a cutter that includes a polycrystalline material body having abonding surface opposing a contact surface; a refractory nitride layerdisposed on the bonding surface of the polycrystalline material body; abonding layer disposed on the refractory nitride layer, the bondinglayer substantially formed by a [111] crystal structure, a [100] crystalstructure, or a combination thereof; and a hard composite bound to thebonding layer opposite the polycrystalline material body with a brazematerial; and

E. a drilling assembly that includes a drill string extendable from adrilling platform and into a wellbore; a pump fluidly connected to thedrill string and configured to circulate a drilling fluid into the drillstring and through the wellbore; and a drill bit attached to an end ofthe drill string, the drill bit having a matrix bit body and a pluralityof cutting cutters according to Embodiments C, D, or both coupled to anexterior portion of the matrix bit body.

Each of embodiments A and B may have one or more of the followingadditional elements in any combination: Element 1: the method furtherincluding forming the bonding layer to have a thickness of 10 microns to250 microns at the bonding surface; Element 2: the method furtherincluding masking the bonding surface of the polycrystalline materialbody or the refractory nitride layer before forming the bonding layer;and removing the mask after forming the bonding layer and before brazingthe bonding layer to the hard composite; Element 3: wherein the hardmaterial is diamond, the bonding layer is substantially formed by the[111] crystal structure of the diamond, and forming the bonding layerinvolves: treating the bonding surface or the refractory nitride layerwith a hydrogen plasma in the presence of oxygen and a carbon-containinggas at 600° C. to 1100° C. at a total pressure 30 torr or greater and agas composition of 200 parts to 250 parts hydrogen, 0.5 parts to 3 partsoxygen, and 3 parts to 8 parts carbon-containing gas; Element 4: whereinthe hard material is diamond, the bonding layer is substantially formedby the [100] crystal structure of the diamond, and forming the bondinglayer involves: treating the bonding surface or the refractory nitridelayer with a hydrogen plasma in the presence of oxygen and acarbon-containing gas at 600° C. to 1100° C. at a total pressure lessthan 30 torr and a gas composition of 200 parts to 250 parts hydrogen,0.5 parts to 3 parts oxygen, and 3 parts to 8 parts carbon-containinggas; Element 5: wherein the hard material is cubic boron nitride; andElement 6: wherein the hard material is silicon carbide.

By way of non-limiting example, exemplary combinations applicable to Aand B: Element 1 in combination with Element 2 and optionally one ofElements 3-6; Element 1 in combination with one of Elements 3-6; andElement 2 in combination with one of Elements 3-6.

Each of embodiments C, D, and E may have one or more of the followingadditional elements in any combination: Element 7:wherein the bondinglayer has a thickness of 10 microns to 250 microns at the bondingsurface; Element 8: wherein the hard material is diamond; Element 9:wherein the hard material is cubic boron nitride; and Element 10:wherein the hard material is silicon carbide.

By way of non-limiting example, exemplary combinations applicable to Aand B: Element 7 in combination with one of Elements 8-10.

One or more illustrative embodiments incorporating the inventionembodiments disclosed herein are presented herein. Not all features of aphysical implementation are described or shown in this application forthe sake of clarity. It is understood that in the development of aphysical embodiment incorporating the embodiments of the presentinvention, numerous implementation-specific decisions must be made toachieve the developer's goals, such as compliance with system-related,business-related, government-related and other constraints, which varyby implementation and from time to time. While a developer's effortsmight be time-consuming, such efforts would be, nevertheless, a routineundertaking for those of ordinary skill in the art and having benefit ofthis disclosure.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered,combined, or modified and all such variations are considered within thescope and spirit of the present invention. The invention illustrativelydisclosed herein suitably may be practiced in the absence of any elementthat is not specifically disclosed herein and/or any optional elementdisclosed herein. While compositions and methods are described in termsof “comprising,” “containing,” or “including” various components orsteps, the compositions and methods can also “consist essentially of” or“consist of” the various components and steps. All numbers and rangesdisclosed above may vary by some amount. Whenever a numerical range witha lower limit and an upper limit is disclosed, any number and anyincluded range falling within the range is specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues. Also, the terms in the claims have their plain, ordinary meaningunless otherwise explicitly and clearly defined by the patentee.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the elements that itintroduces.

The invention claimed is:
 1. A method comprising: forming a bondinglayer on a bonding surface of a polycrystalline material body thatcomprises a hard material, the bonding surface opposing a contactsurface of the polycrystalline material body, and the bonding layersubstantially formed by a [111] crystal structure of the hard material,a [100] crystal structure of the hard material, or a combinationthereof; and brazing the bonding layer to a hard composite using a brazematerial.
 2. The method of claim 1 further comprising: forming thebonding layer to have a thickness of 10 microns to 250 microns at thebonding surface.
 3. The method of claim 1 further comprising: maskingthe bonding surface of the polycrystalline material body before formingthe bonding layer; and removing the mask after forming the bonding layerand before brazing the bonding layer to the hard composite.
 4. Themethod of claim 1, wherein the hard material is diamond, the bondinglayer is substantially formed by the [111] crystal structure of thediamond, and forming the bonding layer involves: treating the bondingsurface with a hydrogen plasma in the presence of oxygen and acarbon-containing gas at 600° C. to 1100° C. at a total pressure 30 torror greater and a gas composition of 200 parts to 250 parts hydrogen, 0.5parts to 3 parts oxygen, and 3 parts to 8 parts carbon-containing gas.5. The method of claim 1, wherein the hard material is diamond, thebonding layer is substantially formed by the [100] crystal structure ofthe diamond, and forming the bonding layer involves: treating thebonding surface with a hydrogen plasma in the presence of oxygen and acarbon-containing gas at 600° C. to 1100° C. at a total pressure lessthan 30 torr and a gas composition of 200 parts to 250 parts hydrogen,0.5 parts to 3 parts oxygen, and 3 parts to 8 parts carbon-containinggas.
 6. The method of claim 1, wherein the hard material is cubic boronnitride.
 7. The method of claim 1, wherein the hard material is siliconcarbide.
 8. A method comprising: depositing a refractory nitride layeron a bonding surface of a polycrystalline material body that comprises ahard material, the bonding surface opposing a contact surface of thepolycrystalline material body; forming a bonding layer on the refractorynitride layer, the bonding layer substantially formed by a [111] crystalstructure of the hard material, a [100] crystal structure of the hardmaterial, or a combination thereof; and brazing the bonding layer to ahard composite using a braze material.
 9. The method of claim 8 furthercomprising: forming the bonding layer to have a thickness of 10 micronsto 250 microns at the bonding surface.
 10. The method of claim 8 furthercomprising: masking the refractory nitride layer before forming thebonding layer; and removing the mask after forming the bonding layer andbefore brazing the bonding layer to the hard composite.
 11. The methodof claim 8, wherein the hard material is diamond, the bonding layer issubstantially formed by the [111] crystal structure of the diamond, andforming the bonding layer involves: treating the refractory nitridelayer with a hydrogen plasma in the presence of oxygen and acarbon-containing gas at 600° C. to 1100° C. at a total pressure 30 torror greater and a gas composition of 200 parts to 250 parts hydrogen, 0.5parts to 3 parts oxygen, and 3 parts to 8 parts carbon-containing gas.12. The method of claim 8, wherein the hard material is diamond, thebonding layer is substantially formed by the [100] crystal structure ofthe diamond, and forming the bonding layer involves: treating therefractory nitride layer with a hydrogen plasma in the presence ofoxygen and a carbon-containing gas at 600° C. to 1100° C. at a totalpressure less than 30 torr and a gas composition of 200 parts to 250parts hydrogen, 0.5 parts to 3 parts oxygen, and 3 parts to 8 partscarbon-containing gas.
 13. The method of claim 8, wherein the hardmaterial is cubic boron nitride.
 14. The method of claim 8, wherein thehard material is silicon carbide.
 15. A cutter comprising: apolycrystalline material body having a bonding surface opposing acontact surface; a bonding layer disposed on the bonding surface, thebonding layer substantially formed by a [111] crystal structure, a [100]crystal structure, or a combination thereof; and a hard composite boundto the bonding layer opposite the polycrystalline material body with abraze material.
 16. The drill bit cutter of claim 15, wherein thebonding layer has a thickness of 10 microns to 250 microns at thebonding surface.
 17. The drill bit cutter of claim 15, wherein the hardmaterial is diamond.
 18. The drill bit cutter of claim 15, wherein thehard material is cubic boron nitride.
 19. The drill bit cutter of claim15, wherein the hard material is silicon carbide.
 20. A drillingassembly comprising: a drill string extendable from a drilling platformand into a wellbore; a pump fluidly connected to the drill string andconfigured to circulate a drilling fluid into the drill string andthrough the wellbore; and a drill bit attached to an end of the drillstring, the drill bit having a matrix bit body and a plurality ofcutting cutters according to claim 6 coupled to an exterior portion ofthe matrix bit body.